1. Field of the Invention
The present invention relates generally to a vehicle lamp. Specifically, embodiments of the present invention relate to an art for surely performing welding in a vehicle lamp in which a housing and a transparent cover provided in front thereof are joined by beam welding.
2. Description of the Related Art
For vehicle lamps, there exists an art of beam welding in which a transparent cover provided in front of a housing is welded onto the housing by irradiation of a beam, such as a laser beam. In joining the housing and the transparent cover by use of beam welding, there are many advantages that cannot be obtained in other joining techniques such as heat plate welding, ultrasonic welding, or bonding.
Meanwhile, in order to surely perform beam welding, the housing and the transparent cover must be placed in close contact at their welding surfaces, and a gap between the welding surfaces must be held within 0.1 mm.
In an effort to place the housing and the transparent cover in proximity with a gap of 0.1 mm or smaller or in close contact at their welding surfaces, it is a common practice to precisely perform a die cutting, an injection condition setting, etc. upon injection-molding of the housing and the transparent cover.
However, it is difficult to actually eliminate post-injection-mold shrink, deflection, deformation, etc., and it is inevitable to encounter regions having a gap of 0.1 mm or greater. Therefore, poor welding results in such regions.
For this reason, there has been an attempt to fix the housing and push the transparent cover toward the housing by a jig so that a forcible deformation can be caused by an external force upon irradiation with a beam, thereby placing both welding surfaces in close contact together at the time of beam welding.
As mentioned above, the housing and the transparent cover can be placed within a gap of 0.1 mm at their welding surfaces in most of the regions by pushing the transparent cover toward the housing with a jig and causing a forcible deformation to the transparent cover by an external force. However, when the transparent cover 70 has a region 75 where a direction of a normal line n1, n2 to the welding surface 73 changes sharply as shown in FIG. 5, structural rigidity in that region increases. In such regions, it is not easy to place the welding surfaces of the transparent cover 70 and the housing 60 within a gap of 0.1 mm even if pushed by a jig.